Yet, as recently as 2012, more than a third of Americans incorrectly believed the virus could be transmitted by sharing a drinking glass with an HIV-positive person, swimming in the same pool as someone infected or even just touching the same toilet seat.

So, even though HIV and AIDS are common terms, myths and confusion clearly remain. So what is HIV, what is AIDS, and what do we know about prevention and treatment?

Here are nine vital facts to know about HIV and AIDS and how to prevent and treat both:

1. HIV is a virus. The Human Immunodeficiency Virus (HIV) attacks the cells in the body (CD4, or T cells) that help the immune system fight off infection. People infected with HIV can become increasingly more susceptible to infections if the virus goes untreated and impairs those immune cells. Like the virus that causes the chicken pox, HIV remains in the body.

2. AIDS is a medical diagnosis; given when an individual has the HIV infection and either a low count of immune cells, an opportunistic infection or both. AIDS is actually the third stage of HIV infection, with the first being exposure to the virus.

3. Known most commonly as Chronic HIV, the second stage is the most critical for treatment. Although exposure to the virus can immediately create flu-like symptoms in some people, many are unaware they have been infected. HIV can be asymptomatic (with no symptoms) for years, but the virus is still attacking the body's immune system, even if the person doesn't feel sick. The CDC recommends antiretroviral treatment for anyone with HIV, which will both minimize the damage to the person's immune system and also reduce the chance of transmission.

4. Transmission is most common among two very specific activities: sexual contact and needle/syringe-sharing. Less commonly, infants born to HIV-positive mothers who did not receive HIV treatment, either through shared blood during pregnancy or while nursing after birth, can be infected.

6. Early treatment and antiretroviral treatment has proven successful in making HIV a chronic condition, instead of the once fatal diagnosis when World AIDS Day began. Yet one in seven Americans who have HIV don't know it. That's why everyone between 13 and 64 should be tested for the virus at least once. People with higher risk factors may need more frequent testing, which they can discuss with their doctor.

7. Despite improvements in treatment for HIV, there is still no cure. Researchers are working to develop a vaccine that would train the body's immune system to fight the virus and prevent it from taking hold. There is also PrEP – or a combination of HIV drugs known as pre-exposure prophylaxis – that can be taken daily to prevent the virus from establishing a permanent infection. It is not 100 percent effective, although it does reduce the risk of infection by more than 90 percent among those who take it properly.

"Across three different studies, including thousands of couples and many thousand acts of sex without a condom or pre-exposure prophylaxis (PrEP)," the statement continues, "no HIV transmissions to an HIV-negative partner were observed when the HIV-positive person was virally suppressed. This means that people who take ART daily as prescribed and achieve and maintain an undetectable viral load have effectively no risk of sexually transmitting the virus to an HIV-negative partner."

8. With the advances in treatment and prevention, HIV/AIDS doesn't generate the headlines it did a generation ago. An estimated 37,600 Americans became infected in 2014, an 18 percent drop nationwide from 2008. Despite that improvement, two populations experience a greater burden of new HIV cases: African-Americans, who accounted for 45 percent of all new infections, and people in the southeastern U.S., who account for roughly half of new infections.

9. Taken together, the facts around HIV/AIDS mean one of the most important factors in effective treatment and prevention of the disease is knowing your HIV status. That requires a test, and World AIDS Day is a good reminder to get one scheduled. Hospitals, community health clinics and many doctors offer HIV tests, or you can visit GetTested to find the closest site for free and confidential testing for HIV, syphilis and other diseases. Those without online access can text their ZIP code to KNOW IT (566948).